The invention is based on a fuel injection apparatus for internal combustion engines as defined hereinafter. In one such fuel injection apparatus, known from German Offenlegungsschrift 36 01 710, a valve triggered by an electromagnet is used to control the onset of injection and the injection quantity; this valve is inserted into a fuel line from the pump work chamber into a low-pressure chamber. By way of the closing and opening of this valve during the pumping stroke of the pump piston, the instant and duration of high-pressure pumping in the pump work chamber and hence of the injection at the injection valve connected to it via an injection line are determined. In order to avert major noise production and pollutant emissions in internal combustion engines that operate with high injection pressure, and above all when injection is done directly into the combustion chamber of the engine to be supplied, where the noise and pollutants are due to the ignition delay at the onset of combustion, the injection quantity is split into a preinjection quantity and a main injection quantity. In this way, at the onset of combustion or in other words when the fuel-air mixture ignites, a slight quantity of fuel is initially injected and prepared by the compressed air in the combustion chamber, and it then burns with a lesser pressure gradient. To that end, in the known fuel injection apparatus the magnet valve closes and then opens immediately again to terminate the preinjection. The magnet valve needle opens only briefly and not completely, and then closes again for the main injection. In order to detect exactly the onset and end of injection, the known fuel injection apparatus has sensors on its injection valve that detect the needle stroke of the injection valve and transmit it to a control unit.
In the known fuel injection apparatus the problem arises that the size of the preinjection quantity, the interval between the preinjection quantity and the main injection quantity, and the main injection quantity cannot be controlled with sufficient precision, since even when the trigger times of the magnet valve are the same, different nozzle opening times and injection quantities result from component drift, temperature changes and fuel tolerances.